Electronic device and rear case of electronic device

ABSTRACT

An electronic device having a heat generating part in an internal space between a front case and a rear case wherein the rear case is integrally molded with a metal sheet and the metal sheet is given relief shapes which increase its surface area, whereby the heat of the heating generating part is dissipated from the rear case and conduction to the front case is reduced. The relief shapes can be formed from a wave shape. The rear case may be made a bathtub shape. Relief shapes of the metal sheet may be exposed at the inside space of the electronic device at the side wall part of the rear case or its vicinity. As a result, the heat which is generated inside the housing of a small electronic device can be efficiently dissipated from the back side and conduction of heat to the front side can be made difficult.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from, and incorporates by reference theentire disclosure of, Japanese Patent Application No. 2013-037561, filedon Feb. 27, 2013.

FIELD

The present application relates to an electronic device which contains aheat generating part wherein the heat which is generated by the heatgenerating part can be passed through a housing to be dissipated andrelates to a rear case of such an electronic device.

BACKGROUND

In recent years, camera, mobile phones, and other small electronicdevices have been spreading in use. As the performance of the ICs(integrated circuits) which are built into these electronic devices isimproved, it has become necessary to enable the heat which the ICsgenerate to escape to the outside of the housing of the electronicdevice.

As the heat dissipating structure of an electronic device, JapaneseLaid-Open Patent Publication No. 2010-191270 discloses to provide a heatdissipating member which is comprised of a metal or other heatconducting material at a back side of a camera with a built-in projectorand to dissipate the heat from the heat generating part through the heatdissipating part to the outside of the camera. Further, JapaneseLaid-Open Patent Publication No. 2001-237577 discloses to provide athrough hole in a housing at a lower side of the board which mounts theelectronic components, attach inside of this through hole a heatdissipating part which is made by a metal material, and dissipate theheat which is generated from the electronic component to the outside ofthe housing. Furthermore, Japanese Laid-Open Patent Publication No.2004-281977 discloses to provide a plurality of through holes at thepart of the housing of the electronic device where heat dissipation isrequired, spray molten metal particles from outside of the through holesto build up at the through holes and outer surface and form a heatdissipating part, and dissipate heat which was generated at the insideto the outside.

On the other hand, in an electronic device such as a mobile phone(including smart phones), when there is a waterproofing structurebetween the front case and rear case, the battery is arranged at therear case and is covered by a battery cover. FIG. 1A is a view of asmart phone 10 of the related art as seen from the front side. Thehousing 11 is provided with a front case 1 at which a display 13 isprovided, a rear case 2, and a battery cover 3 which is detachablyattached to the rear case 2. FIG. 1B is a view of the smart phone 10which is illustrated in FIG. 1A as seen from the back side. The shape ofthe battery cover 3 which is attached to the rear case 2 can beunderstood from this figure.

In this regard, the smart phone 10 of the structure which is explainedfrom FIG. 1A to FIG. 1C is a structure where, due to the followingfactors, the heat which is generated at the electronic component 8 iseasily conducted to the liquid crystal panel 4 at the front case 1.

-   Factor 1: The heat source is at front case 1 side.-   Factor 2: A metal sheet 5, which easily conducts heat, is integrally    formed with the front case 1. This is because the rear case 2 which    forms the back side is mostly formed by an opening part due to the    battery 9 being housed and therefore is weak in strength, so the    strength of the overall set of the smart phone 10 is made up for by    the front case 1.-   Factor 3: There is a battery cover 3, so there is an air layer    between the heat which is trapped inside the set and the outside to    which the heat is desired to be dissipated and therefore conduction    of the heat to the back side is difficult.

FIG. 1C is a cross-sectional view in the short direction of the smartphone 10 which is illustrated in FIG. 1A and FIG. 1B. It explains theinternal structure of a smart phone 10 of the related art. The shapes ofthe members do not match the shapes of the members which are illustratedin FIG. 1A and FIG. 1B. At the top surface of the front case 1 of thesmart phone 10, a liquid crystal panel 4 is attached. Below the liquidcrystal panel 4, there is a liquid crystal module 6 which is supportedby a metal sheet 5 which is formed integrally with the front case 1. Thefront case 1 is made of plastic, while the metal sheet is made of metal.Further, in the rear case 2, there is a circuit board 7. On the topsurface of the circuit board 7, an electronic component 8 is mounted.The electronic component 8 is an integrated circuit or other mountedpart and acts as a heat source. Further, inside of the rear case 2, abattery 9 is housed. The battery cover 3 is attached to the rear case 2.

Note that, in the smart phone 10 which is illustrated as related art,waterproofing packing is attached between the front case 1 and the rearcase 2 etc. so as to prevent water from entering the inside, butillustration is omitted in FIG. 1B.

In this way, in the smart phone 10 of the related art, the heat at theinside of the housing 11 is easily conducted to the front side. Thefront side directly contacts the human body, so there was the issue of alarge risk of low temperature burns etc. Further, in the case of a smartphone 10 which has a waterproofing structure, the housing 11 is high inair-tightness, and heat easily is trapped inside of the housing 11. Forthis reason, in a smart phone, it is desirable that the heat which isgenerated at the inside be hard to contact the human body and beefficiently dissipated to the outside.

SUMMARY

In one aspect, the present application has as its object the provisionof a small electronic device such as a smart phone which can efficientlydissipate heat which is generated inside a housing from a back side andmake conduction of heat to the front side difficult. In another aspect,the present application has as its object the provision of a rear caseof a small electronic device such as a smart phone which can efficientlydissipate heat which is generated inside a housing from a back side andmake conduction of heat to the front side difficult.

According to one aspect of the embodiment, there is provided anelectronic device which is provided with a front case and a rear caseand which is provided with a heat generating part in an internal spacewhich is surrounded by the front case and the rear case, in whichelectronic device, a metal sheet is integrally molded with the rear caseand the metal sheet is given relief shapes which increase the lengthfrom one end to another.

According to another aspect of the embodiment, there is provided a rearcase of an electronic device which is provided with a heat generatingpart in an inside space which is surrounded by a front case and rearcase, in which rear case of an electronic device, a metal sheet isintegrally molded with the rear case and the metal sheet is given reliefshapes which increase the length from one end to another.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a perspective view of a smart phone of one example of amobile terminal device as seen from a front side.

FIG. 1B is a perspective view of the smart phone which is illustrated inFIG. 1A as seen from a rear side.

FIG. 1C is a cross-sectional view along a short direction of the smartphone which is illustrated in FIG. 1A and FIG. 1B.

FIG. 2A is a cross-sectional view which illustrates a structure of anelectronic device of a first embodiment of the present application.

FIG. 2B is a see-through view which illustrates a structure of a rearcase unit of the electronic device which is illustrated in FIG. 2A.

FIG. 3A is a cross-sectional view which illustrates the structure of anelectronic device of a second embodiment of the present application.

FIG. 3B is a perspective view which illustrates a structure of metalsheet which is contained in a rear case of the electronic device whichis illustrated in FIG. 3A.

FIG. 4A is a back view of an electronic device as seen from its backside.

FIG. 4B is a plan view of a metal sheet which is contained in the rearcase which is illustrated in FIG. 4A.

FIG. 4C is a cross-sectional view along a line C-C of the metal sheetwhich is illustrated in FIG. 4B.

FIG. 4D is a partial cross-sectional view of a part A of the electronicdevice which is illustrated in FIG. 4B.

FIG. 5A is a partial enlarged cross-sectional view which illustratespart of the process for producing a rear case of an electronic device ofa third embodiment of the present application.

FIG. 5B is a cross-sectional view which illustrates a rear case of anelectronic device of the third embodiment which is produced by themethod of production of FIG. 5A.

FIG. 6A is a cross-sectional view of a rear case which is used in anelectronic device of a fourth embodiment of the present application.

FIG. 6B is a cross-sectional view of a rear case which is used in anelectronic device of a fifth embodiment of the present application.

FIG. 6C is a cross-sectional view of a rear case which is used in anelectronic device of a sixth embodiment of the present application.

FIG. 6D is a cross-sectional view of embossed metal sheet which iscontained in a rear case which is used in an electronic device of aseventh embodiment of the present application.

DESCRIPTION OF EMBODIMENTS

Below, the attached drawings will be used to explain in detail theembodiments of the present application based on specific examples. Notethat, component members which are the same as the component memberswhich are used for the smart phone of the related art which wasillustrated in FIG. 1C are assigned the same notations for theexplanation.

FIG. 2A is a cross-sectional view which illustrates the structure of asmart phone 21 of an electronic device of a first embodiment of thepresent application. At the top surface of a front case 1 of the smartphone 21, a liquid crystal panel 4 is attached. Below the liquid crystalpanel 4, there is a liquid crystal module 6 which is supported by ametal sheet 5 which is integrally molded with a side wall part 1W of thefront case 1. The front case 1 is made of plastic, while the metal sheetis made of metal. Further, a rear case 2 of the smart phone 21 is plateshaped and is provided with a side wall part 2W with an edge raised tothe front case 1 side. This side wall part 2W is joined with the sidewall part 1W of the front case 1. The joined part of the side wall part1W and the side wall part 2W is provided with a waterproofing packingetc., but this is not illustrated in this figure. At the inside space 20of the rear case 2 and the metal sheet 5, there is a circuit board 7. Onthe top surface of the circuit board 7, an electronic component 8 ismounted. The electronic component 8 is an integrated circuit or othermounted part and is a heat generating element. Further, at the bottomsurface of the circuit board 7, a battery 9 is attached.

In the present application, a metal sheet 30 is embedded in theplate-shaped rear case 2. FIG. 2B is a see-through view whichillustrates a structure of a rear case 2 unit of the smart phone 21which is illustrated in FIG. 2A and illustrates an embodiment of theshape of the metal sheet 30 which is contained in the rear case 2. Whenembedding the metal sheet 30 in the rear case 2, if using a knowninjection molding machine, the metal sheet 30 is embedded in the rearcase 2 by integral molding. The metal sheet 30 which is embedded in therear case 2 is provided with a bottom part 30B and a wall part 30Wmatched with the shape of the rear case 2.

Further, the shape of the metal sheet 30 which is embedded in the rearcase 2 is not a flat plate shape, but is a shape which is given reliefshapes which increase the surface area of the metal sheet 30. The shapeof the metal sheet 30 of the smart phone 21 of the first embodiment is across-sectional wave shape formed in the horizontal direction (shortdirection) of the smart phone 21 and has recessed parts 31 andprojecting parts 32. The recessed parts 31 and projecting parts 32 areprovided with periodicity and appear alternately in the horizontaldirection (short direction) of the smart phone 21. The wave shape of themetal sheet 30 may also be formed in the vertical direction (longdirection) of the smart phone 21.

In the smart phone 21 of the first embodiment, the heat which isgenerated by the heat source constituted by the electronic component 8is conducted to the metal sheet 30 which is embedded in the rear case 2and is dissipated from the bottom part 30B to the wall part 30W, so theheat can be easily released to outside of the rear case 2. That is, itis possible to reduce the influence of the above-mentioned factor 2 tothe front side of the smart phone 21. Further, by making the metal sheet30 a wave shape so as to increase the surface area, it becomes possibleto raise the heat dissipation effect.

FIG. 3A is a cross-sectional view which illustrates the structure of anelectronic device of a second embodiment of the present applicationconstituted by a smart phone 22. The smart phone 22 of the secondembodiment is provided with a rear case 2 of a bathtub structure. Nofront case is provided. The side wall part 2W of the rear case 2 of thebathtub structure is high in height. The liquid crystal panel 4 isdirectly attached by a binder 18 to the side wall part 2W of the rearcase of the bathtub structure. Instead of the binder 18, two-sided tapemay also be used.

At an inside space 20 which is surrounded by the liquid crystal panel 4and the bottom part 2B of the rear case 2, a liquid crystal module 6which is supported by a metal sheet 5 and a circuit board 7 on which anelectronic component 8 is mounted are provided. Further, at the bottompart 2B of the rear case 2, a battery 9 is attached. The positions ofthe circuit board 7 on which the electronic component 8 is mounted andthe battery 9 which are arranged in the inside space 20 which issurrounded by the liquid crystal panel 4 and the bottom part 2B of therear case 2 are not limited to these positions. The positions may bereversed.

In the smart phone 22 of the second embodiment, a metal sheet 30 isembedded at the bottom part 2B and side wall part 2B of the bathtubstructure rear case 2. FIG. 3B illustrates one embodiment of the shapeof the metal sheet 30 which is embedded in the rear case 2 which isillustrated in FIG. 3A. When embedding the metal sheet 30 in the rearcase 2, if using a known injection molding machine, the metal sheet 30is embedded in the rear case 2 by integral molding. The metal sheet 30which is embedded in the rear case 2 is provided with a bottom part 30Band wall part 30W matching the rear case 2 of the bathtub structure.

The shape of the metal sheet 30 is not a flat plate shape, but is ashape which is given relief shapes which increase the surface area ofthe metal sheet 30. The shape of the metal sheet 30 of the smart phone22 of the second embodiment is a cross-sectional wave shape formed inthe horizontal direction (short direction) of the smart phone 22 and hasrecessed parts 31 and projecting parts 32. The recessed parts 31 andprojecting parts 32 are provided with periodicity and appear alternatelyin the horizontal direction (short direction) of the smart phone 22. Thewave shape of the metal sheet 30 may also be formed in the verticaldirection (long direction) of the smart phone 22 or in a combined shapeat both, at a slant, etc. Further, the wall part 30W may also bearranged at all of the four sides of the bottom part 30B.

In a smart phone 2 which uses a bathtub structure rear case 2, thebattery and other parts which have to be taken out or the externalterminals etc., while not illustrated, should be structured to be takenout at the side face of the rear case 2. In the smart phone 22 of thesecond embodiment, the heat which is generated by the heat sourceconstituted by the electronic component 8 is conducted to the metalsheet 30 which is embedded in the rear case 2 where it is dissipatedfrom the bottom part 30B to the wall part 30W, so the heat is easilydissipated to the outside of the rear case 2. That is, it is possible toreduce the influence of the above-mentioned factor 2 of heat beingeasily conducted to the front side of the smart phone 22. Further, bymaking the metal sheet 30 a wave shape and extending it to the side wallpart 2W of the rear case 2 to increase the surface area, it becomespossible to greatly enhance the heat dissipation effect.

FIG. 4A is a view of a smart phone 23 as seen from the back side. Thissmart phone 23 is provided with an opening part 12 at the side surfacefor emitting sound from the speaker. When, in this way, the back surfaceof the smart phone 23 is provided with the opening part 12, asillustrated in FIG. 4B, the portion of the metal sheet 30 which isembedded in the rear case 2 which corresponds to the position of theopening part 12 is formed at the flat part 30F. Further, the part wherethe flat part 30F overlaps the opening part 12 is provided with athrough hole 33. FIG. 4C illustrates the cross-sectional shape of themetal sheet 30 along the line C-C of FIG. 4B. The part of the metalsheet 30 other than the flat part 30F is provided with relief shapes ofa wave shape in the same way as the first embodiment.

Furthermore, FIG. 4D is a cross-sectional view which illustratespartially enlarged a part A of the smart phone 23 which is illustratedin FIG. 4B. When the rear case 2 is a bathtub structure, the back sideof the rear case 2 is provided with an opening part 12 of a speakeretc., but the opening part 12 may be dealt with by providing a flat part30F at the integral molded metal sheet 30 and exposing part of the metalsheet 30. That is, when the back surface of the smart phone 23 isprovided with the opening part 12, the part of the metal sheet 30 whichis embedded in the rear case 2 which corresponds to the opening part 12is formed at the flat part 30F and this flat part 30F is provided with athrough hole 33. The through hole 33 can be provided by utilizing thepositioning hole which is formed at the time of molding the rear case 2.In this embodiment, at the inside of the rear case 2 which correspondsto the opening part 12, a speaker 14 is provided. The sound from thespeaker 14 is emitted to the outside through the through hole 33 of themetal sheet 30.

Further, when the smart phone 23 is a waterproof specification, the flatpart 30F of the metal sheet 30 around the through hole 33 is providedwith a waterproof mesh 15 which passes sound, but does not passmoisture. Further, the rear case 2 around the opening part 12 isprovided with heat activated waterproof tape with the flat part 30F ofthe metal sheet 30. Moisture is prevented from entering inside the rearcase 2 by this. Note that, by using a metal sheet which is coated on itssurface with a plastic, the heat activated waterproof tape 16 can alsobe omitted.

Further, when the rear case 2 is a bathtub structure, since the sidewall part 2W of the rear case 2 is high in height, there is apossibility of the metal sheet becoming loose at the time of molding therear case 2. In such a case, it is sufficient to place a holdingstructure in the mold. This will be explained while using FIG. 5A andFIG. 5B.

FIG. 5A is a partial enlarged cross-sectional view which illustratespart of the process for producing the rear case 2 of the electronicdevice of the third embodiment of the present application. Illustrationof the mold for forming the rear case 2 as a whole will be omitted, butwhen preventing the metal sheet from becoming loose at the time ofmolding the rear case 2, the mold may be provided with a slide mold 17.The slide mold 17 is generally attached to the male half of the mold. Ininsert molding, the slide mold 17 holds down the wall part 30W of themetal sheet until the plastic is injected between the female half andmale half. Further, after the injection molding is finished, the slidemold 17 moves in the direction which is illustrated by the arrow, so therear case 2 in which the metal sheet 30 is embedded can be detached fromthe male die.

Note that, the slide mold 17 slides in the direction which isillustrated by the arrow after injection molding, so the part of themetal sheet 30 where the slide mold 17 moves requires an exposed part30E which is exposed at the inside of the rear case 2. The part of themetal sheet 30 other than where the slide mold 17 moves, as illustratedin FIG. 5A, is embedded inside of the rear case 2 in the same way as theabove-mentioned embodiment and is embedded in the state provided withthe recesses 31 and projections 32. FIG. 5B is a cross-sectional viewwhich illustrates a rear case 2 which is used in the smart phone of thethird embodiment which is produced by the method of production which isillustrated in FIG. 5A. If, in this way, there is an exposed part 30E ofthe metal sheet 30 at the inside surface of the rear case 2, conductionof the heat which is generated inside of the smart phone to the metalsheet 30 becomes easy and the conduction of heat to the front side issuppressed more.

Above, several examples of the structure of the rear case of the presentapplication which was used for a smart phone were explained, but theshape of the relief shapes of the metal sheet which is embedded in therear case is not limited to the above embodiment. Other shapes of therelief shapes of the metal sheet will be further explained using FIG. 6Ato FIG. 6D.

FIG. 6A illustrates the cross-section of a rear case 2 which is used fora smart phone of a fourth embodiment of the present application. In thefourth embodiment, the relief shapes which are formed at the metal sheet30 are formed by a cross-sectional pulse wave shape which has recessedparts 31 and projecting parts 32 in either direction of the horizontaldirection and vertical direction of the smart phone. The recessed parts31 and the projecting parts 32 are repeatedly formed by a certainperiod. Note that, the boundary parts 34 of the recessed parts 31 andprojecting parts 32 of this embodiment rise up vertically with respectto the recessed parts 31 and projecting parts 32, but they may also beshapes which rise in a slanted direction. Further, the recessed parts 31and projecting parts 32 may also be shapes combining ones in both thehorizontal direction and vertical direction or including the slanteddirection etc. in combination.

FIG. 6B illustrates the cross-section of a rear case 2 which is used fora smart phone of a fifth embodiment of the present application. In thefifth embodiment, the metal sheet 30 which is provided with the pulsewave shape cross-section which is illustrated in FIG. 6A is furtherprovided with relief parts 35 at the boundary parts 34 of the recessedparts 31 and projecting parts 32. The relief parts 35 at the boundaryparts 34 of the recessed parts 31 and projecting parts 32 can be formedby crushing the two sides of the projecting parts 32 by a fixture. Inthis way, by further providing relief parts 35 at the boundary part 34of the recessed parts 31 and projecting parts 32, the plastic willbecome rooted in the metal sheet 30 and the adhesion of the plastic andmetal sheet 30 will be raised. Due to this, it is possible to make therear case 2 one which is provided with a high heat dissipating effectand a high strength.

FIG. 6C illustrates the cross-section of a rear case 2 which is used fora smart phone of a sixth embodiment of the present application. In thefourth embodiment, the cross-sectional pulse wave shape relief shapeswhich were formed at the metal sheet 30 were formed by the same period.On the other hand, in the sixth embodiment, the cross-sectional pulsewave relief shapes which are formed at the metal sheet 30 are denser atsome parts and sparser at other parts. That is, in the sixth embodiment,the period of repetition of the cross-sectional pulse wave shape reliefshapes is not constant. When making the period of repetition of thecross-sectional pulse wave shape relief shapes different in this way, itis considered that if making the period shorter the closer the locationto the source of generation of heat in the smart phone, the heatdissipation effect would be large. The period of the relief shapes whichare formed at the metal sheet 30 may be changed in the cross-sectionalwave type relief shapes which were explained in the first to thirdembodiments.

FIG. 6D illustrates a cross-section of the rear case 2 which is used fora smart phone of a seventh embodiment of the present application. In theseventh embodiment, the metal sheet 30 is provided with a plurality ofembossed parts 36 so as to provide the metal sheet 30 with reliefshapes. The embossed parts 36 may be provided so as to stick out only atone surface of the metal sheet 30. Further, as illustrated in FIG. 6D,they may be provided to stick out at both surfaces of the metal sheet30. Furthermore, the embossed parts 36 may be formed arranged in severallines on the metal sheet 30. Further, they may be randomly formed on themetal sheet 30.

As explained above, according to the electronic device and the rear caseof the electronic device of the present application, there are thefollowing effects:

-   (1) Due to dissipation of heat which is generated inside of the    housing to the back side of the rear case, conduction of heat to the    front side is prevented.-   (2) Due to metal sheet being embedded in the rear case, the strength    of the rear case is improved.-   (3) Due to elimination of the battery cover etc., the number of    parts is slashed and the cost is cut.-   (4) Due to no waterproof packing being used, the water stopping    performance can be improved.-   (5) The electronic device, in particular a smart phone, can be    reduced in thickness and size, simplified in assembly, and decreased    in number of work hours for assembly.

Although only some exemplary embodiments of this invention have beendescribed in detail above, those skilled in the art will readilyappreciate that many modifications are possible in the exemplaryembodiments without materially departing from the novel teachings andadvantages of this invention. Accordingly, all such modifications areintended to be included within the scope of this invention.

What is claimed is:
 1. An electronic device comprising: a front case anda rear case; a heat generating part provided in an internal space whichis surrounded by the front case and the rear case; and a metal sheetembedded in the rear case by integral molding which is given reliefshapes for increasing the surface area thereof.
 2. The electronic deviceaccording to claim 1, wherein said relief shapes are formed by a waveshape formed in either direction of a horizontal direction and verticaldirection of said electronic device.
 3. The electronic device accordingto claim 1, wherein said relief shapes are formed by a cross-sectionalpulse wave shape which has recessed parts and projecting parts in eitherdirection of a horizontal direction and vertical direction of saidelectronic device.
 4. The electronic device according to claim 3,wherein boundary parts of recessed parts and projecting parts of saidrelief shapes of the pulse wave shape are further formed with reliefshapes.
 5. The electronic device according to claim 1, wherein saidrelief shapes are formed by embossing.
 6. The electronic deviceaccording to claim 2, wherein the relief shapes of said wave shape andthe relief shapes of the pulse wave shape are formed in either directionof a horizontal direction and vertical direction of said electronicdevice by a predetermined period.
 7. The electronic device according toclaim 6, wherein said predetermined period is shorter the closer thelocation to the source of generation of the heat in said electronicdevice.
 8. The electronic device according to claim 1, wherein said rearcase is a bathtub type.
 9. The electronic device according to claim 8,wherein the relief shapes of the metal sheet are exposed at an insidespace of said electronic device at the side wall part of the rear caseand its vicinity.
 10. The electronic device according to claim 1,wherein said electronic device is a waterproof specification and, whensaid rear case is provided with an opening part, said metal sheetcorresponding to the opening part of said rear case is formed flat, athrough hole corresponding to said opening part is formed, and saidthrough hole is covered by a waterproofing member.
 11. A rear case of anelectronic device which is provided with a heat generating part in aninside space which is surrounded by a front case and rear case, in whichrear case of an electronic device, a metal sheet is integrally moldedwith the rear case and the metal sheet is given relief shapes whichincrease the surface area.
 12. The rear case according to claim 11,wherein said relief shapes are formed by a wave shape formed in eitherdirection of a horizontal direction and vertical direction of saidelectronic device.
 13. The rear case according to claim 11, wherein saidrelief shapes are formed by a cross-sectional pulse wave shape which hasrecessed parts and projecting parts in either direction of a horizontaldirection and vertical direction of said electronic device.
 14. The rearcase according to claim 13, wherein rising parts and falling parts ofrecessed parts of the pulse wave shape are further formed with reliefshapes.
 15. The rear case according to claim 11, wherein said reliefshapes are formed by embossing.
 16. The rear case according to claim 11,wherein the relief shapes of said wave shape and the relief shapes ofthe pulse wave shape are formed in either direction of a horizontaldirection and vertical direction of said electronic device by apredetermined period.
 17. The rear case according to claim 16, whereinsaid predetermined period is shorter the closer the location to thesource of generation of the heat in said electronic device.
 18. The rearcase according to claim 11, wherein said rear case is a bathtub type.19. The rear case according to claim 18, wherein the relief shapes ofthe metal sheet are exposed at an inside space of said electronic deviceat the side wall part of the rear case and its vicinity.
 20. The rearcase according to claim 11, wherein said electronic device is awaterproof specification and, when said rear case is provided with anopening part, said metal sheet corresponding to the opening part of saidrear case is formed flat, a through hole corresponding to said openingpart is formed, and said through hole is covered by a waterproofingmember.